12)A rocket is fired vertically up from yhe ground with a resultant vertical acceleration of 10m/s2. the fuel is finished in 1 min and the rocket continues to move up.after how much time from then will the max. height b reached?(g=10m/s2)?
1)An astronaut jumps from an aeroplane.after he had fallen 40m,then his parachute opens.Now he falls with a retardation of 2m/s2 and the earth with a velocity of 3m/s.What was the height of the the aeroplane?For how long astronaut remained in air?
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4 Answers
1
6240=1/2 g t2
t=√80/9.8=√400/49=20/7
his velocity at that time is gt=28m/s
Then there is retardation of 2 m/s2... so
32=282-2gS
S=25x31/(2x9.8)
Total height will be S+40
For time, 3=28-2t, t=25/2
Total time = 25/2+20/7
622)A rocket is fired vertically up from yhe ground with a resultant vertical acceleration of 10m/s2. the fuel is finished in 1 min and the rocket continues to move up.after how much time from then will the max. height b reached?(g=10m/s2)?
in 60 secs.. the speed is equal to 60t=600m/s
Now it faces retardation of of 10m/s2.. so its speed will come back to zero in another 60 seconds
After that the speed will be -ve or it will be headed towards the earth..
Hence the time is 120 sec = 2 mins
* I have ignored the fact that g changes with height..
1after how much time from then will the max. height b reached?(g=10m/s2)?
@ Nishant Bhaiya : I think u missed the phrase "from then".
else i'm getting answer 1min.
Method is absolutely correct ( LOL.....who am i to comment ;-) )